The present invention relates to a rubber closure device for a vial and more particularly to a rubber closure device for sealing the mouth of a vial or like vessel which is resistant to chemicals and can preferably be used in association with a vacuum-filled vial.
The rubber vial closure devices available in the past are made of materials which are resistant to chemicals and have sealing effects or are made of two different materials in order to prevent degradation of the pharmaceutical product contained in the vial, e.g. discoloration, flocculation opalescence or precipitation of the contents or a decrease in potency of the active component. An example of such closure device is disclosed in any one of, for example, Japanese Utility Model Publication Nos. 3893/1951, 17831/1970 and 9095/1972; and French Pat. No. 75922 and is an improved rubber closure device comprising a rubber closure body made of natural rubber or an equivalent material and a thin layer of polypropylene, polyethylene, chloroprene or the like as laminated with the surface of said body which surface is apt to come in contact with a medicament of the vial. However, if this closure device is used in association with a vacuum-filled vial, the rubber component of said body undergoes leakage thereby failing to ensure adequate resistance to chemicals. The other closure devices involving a teflon layer on the surface contacting the medicament of the vial, such as disclosed in any one of Japanese Laid-Open Utility Model Application (Unexamined) No. 41642/1973 and U.S. Pat. No. 3,552,591 serve the purpose of resisting chemicals, but are too expensive and hardly lend themselves to high production, thus being virtually useless for mass-marketing pharmaceutical products.
It has come to the attention of the present inventors that fluorinated rubber is so resistant to chemicals that this property, taken together with other beneficial properties, make it a desirable material for use as vial closure devices. The inventors accordingly have built a vial closure device of this material and submitted it to a series of tests. However, while the closure device of this type was more or less gas-impermeable at atmospheric pressure, it was found to be permeable to gases under reduced pressure as in a vacuum-filled vial. It was also found to be inferior as a closure device in terms of resealing and coring properties. Therefore, the present inventors have made improvements on the device and finally perfected a new closure device invention which withstands use under a decompressed state, for instance, within a vacuum-filled vial.